1. Field of the Invention
This invention relates generally to air filter media and more particularly to a composite air filter media that incorporates a layer of low surface free energy netting laminated to its upstream surface for improved dust-releasing properties.
2. Description of the Related Art
Modern air filter media used in vacuum cleaners and portable air cleaner applications are typically constructed from expanded microporous membranes such as polytetraflouroethylene (PTFE), or non-woven meltblown synthetic fibers that are calendered and coated with hydrophobic material. These media are preferred for their ability to be effectively regenerated by shaking and/or tapping the filter unit's frame against a solid surface, or by vacuuming the upstream surface of the filter, for example. The PTFE surface free energy is relatively low, in the range of 20 mN/m, as is the hydrophobic (fluorochemically) coated material (22-24 mN/m), which enhances removal of particles during regeneration.
Filters made from expanded microporous membranes or meltblown fibers treated with hydrophobic material, however, are expensive, exhibit high pressure drops, and have upstream surfaces that are susceptible to abrasion as compared to other types of paper media or synthetic non-woven fiber media. It would therefore be advantageous to have a filter media that is less expensive, more efficient, and more durable than media made from microporous membranes or treated meltblown, but that possesses similar regenerative properties.